the code of conduct

@jxson @flores @davidguttman

Wanted to know what y'all thought about having a code of conduct. We have a pretty cool community, but there can always be some bad people out there and thought that we should let the community know where we stand on bad behavior. 

I looked at both the [pycon code of conduct](https://github.com/python/pycon-code-of-conduct/blob/master/code_of_conduct.md) and the [rust code of conduct](https://github.com/mozilla/rust/wiki/Note-development-policy#conduct). I used http://geekfeminism.wikia.com/wiki/Conference_anti-harassment/Policy as a template, which is CC0 / public domain.